Field of the Invention
The invention relates generally to downhole electric equipment, and more particularly to systems and methods for improving the reliability electrical connections between power cables and the windings of motors for electric submersible pumps (ESP's).
Related Art
Electric submersible pump (ESP) systems are commonly positioned in wells and used to pump fluids (e.g., oil) from the wells. AC power that is suitable to drive the ESP systems is produced at the surface of the wells and is delivered to the ESP systems via power cables that extend into the wells. The power cables are typically spliced to motor lead extensions, which are in turn connected to the motor of the ESP using a “pothead” connector. Within the housing of the ESP's motor, flexible leads are coupled between the pothead connector and the motor windings in the motor's stator.
In a conventional ESP, the lower ends of the flexible leads within the motor are connected to the stator windings and are wrapped with a dielectric tape before being encapsulated in epoxy. The flexible leads extend upward out of the epoxy encapsulant through an epoxy fixture. The upper ends of the flexible leads are crimped to terminal pins that are positioned with an insulating block that is positioned in an aperture through the motor head. The pothead connector is fastened to the motor head over this aperture, connecting the flexible leads to the motor lead extension.
The interior of the motor, including the volume through which the flexible leads extend, is typically filled with dielectric oil to allow the pressure inside the motor to be equalized to the pressure external to the motor and to provide additional insulating properties. The i-block is designed to allow oil from the motor to flow between the i-block and the motor head, thereby filling any open spaces within the junction of the pothead connector and the motor terminals. One of the problems with this configuration is that, as the motor is operated, contaminants such as water and small debris particles in the oil may accumulate at the pothead junction. This may eventually cause short-circuits between different conductors within the junction, resulting in corresponding power failures.
The connection of the flexible leads to the motor windings presents another problem in the conventional design. When the motor is being constructed and tested, it may be discovered that there are one or more faults in the electrical pathway between the power cable and the motor windings. Because the connection between the flexible leads and the motor windings is embedded in the epoxy encapsulant, it is very difficult, if not impossible, to replace or repair the flexible leads and the connections to the motor windings. If the faults cannot be repaired, the motor itself may have to be scrapped, which is very costly.
It would therefore be desirable to provide improved means for coupling the motor windings to the conductors of the power cable.